Area of Attraction and Effective Area Fished by a Whelk (<i>Buccinum undatum</i>) Trap under Variable Conditions

Abstract

A study was conducted to examine the size and shape of the area of attraction, to evaluate the effective fishing area of a whelk (Buccinum undatum) trap under different physical and biotic conditions, and to validate the whelk density estimates as determined from the effective area. The study was conducted using a tag–recapture method in the Archipel de Mingan, Quebec. The effect of six different variables was examined (season, bait, depth, substratum, current, and stress). Current speed and direction were shown to be important in defining the size and shape of the area of attraction. Estimates of the effective area ranged from 18 to 278 m 2 . Lowest values were associated with relatively strong currents (26 cm∙s −1 ), while highest values were observed in July and when a less stressful tagging procedure was used. Behavioural factors, notably seasonal variations in feeding rates and reproductive activity, also appeared to affect the size of the effective area. Density estimates derived from the effective areas were comparable with SCUBA diving survey estimates. Our study shows that the effective area cannot be estimated as a single, gear-specific value. Effective area estimates must therefore be determined on a site- and season-specific basis if conditions affecting the catchability of whelks vary during the fishing season and/or over the fishing area.